Method of making bodies of cork



Patente d Nov. 18, 1947 UNITED STATES PATENT OFFICE METHOD OF MAKING BODIES CORK Josef Ehrlich, New York, N. Y.

No Drawing. Application September 14, 1944, Serial No. 554,157

1 Claim. 1 My Invention relates to a new and improved method of making bodies. The invention relates particularly to the manufacture of bodies which are made of cork, cork wood, or mixtures there of. It includes the manufacture of bodies which are made of any other materials which can be shaped by pressure. Said materials are preferably, but not necessarily carbonizable. Cellulosic materials are included within the class of carbonizable materials.

The invention relates particularly to the manufacture of what is known as insulation cork. This insulation cork is used extensively whenever heat insulation is required, as in refrigerators, etc. This product is also referred to in the trade as insulation corkboard.

According to one Well-known method of making such insulation corkboard, the raw material is cork wood which is stripped from cork trees, intermixed with cork waste. This cork wood is designated as virgin and refuge, the former being the bark of the first stripping, and the latter being the bark which is secured from subsequent stripping of the tree.

According to current practice, the cork wood and the cork waste are ground, and the intermixed ground material is compressed in metal molds. While held under pressure in said metal molds, the material is baked during a period of 6 hours-l2 hours, at a temperature of 500 F.-600 F., namely, 260 C. to 315 C.

In another well-known alternative process, said loaded molds are attached to steam lines, which supply superheated steam, in order to heat the ground intermixed material which is held under pressure in the molds. The steam baking process is completed during a relatively short period of 15-20 minutes, at a temperature of about 600 F., namely 315 C.

In both of these known processes, the natural resins in the cork and/or cork wood provide the necessary binder for connecting the particles of said starting material. The above methods are also used in order to make insulation bodies from cork granules of large size. In such case, the natural resins in the corkitself provide the binder. It is likely that. under the high temperature above-mentioned, the natural resins are driven out of the capillary spaces of the cork or other raw material. Said resins are apparently at least partially burned or carbonized. It is likely that said carbonization is only partial. The cork and/r cork wood seems to be partially carbonized, because the final product is discolored and it has a burnt smell. This heat treatment results in a loss of about 20% of the original Weight of the starting material, especially if it is granular cork. Likewise, during the application of the heat and pressure, a blue smoke escapes from the raw material, thus evidencing that there is some burning or oxidation. It is believed by the trade that the heat insulation properties of the material are better, if the finished product has a partly charred appearance.

Said long period of dry heating or baking, without the use of steam, is required because ordinarily a cubical block whose Volume is one cubic yard is manufactured, and it takes time for the heat to penetrate to the interior of such cubical block.

Another application of cork blocks, made of pure granular cork, is for use as shell plugs in ordnance. Such cork shell plugs must completely disintegrate, when the shell is fired. The partial charring of the cork probably faciliatates such disintegration. Therefore, in making shell plugs, the heat is applied for an even longer period than in making bodies of insulation cork. My invention applies to said shell plugs.

According to my invention, I can decrease both the time and the temperature of the heat treatment. Likewise, I can produce cork bodies of superior quality for making either bodies of insulation cork or shell plugs. In the preferred embodiment of my method, I use dry heat or baking, instead of applying the heat by means of steam. However, the invention is not limited to any particular method of applying the heat. Thus, I can heat the mass of material in the mold by means of steam, and I can also heat said material electrically, as later described herein.

According to my invention, I can diminish the temperature of heating, either in making bodies of insulation cork or shell plugs, to 400 F.-4.50 F., namely, 205 C.-232 C. Whenever I state any specific figures herein, this is only by way of illustration, and the invention is not limited thereto, or to any of the details stated herein.

According to one embodiment of my invention, I coat the particles of cork wood and/or cork waste, with suitable mineral salts, prior to applying the heat and pressure. These mineral salts are preferably chlorides and more particularly metallic chlorides. The best of these chlorides is ammonium chloride, which, according to the tests I have made, is far superior to every other chloride. As later stated herein, ammonium chloride is not hygroscopic. It is largely driven ofi in my process, but it acts to facilitate the decomposition of the ammonium nitrate. However, I can use sodium chloride, potassium chloride, etc. These chlorides can be used singly, or intermixed. As later described, I can use mixtures of said chlorides and other ingredients, as the added material.

I coat the particles with said chlorides or other added materials by spraying the particles at about 70 F. with an aqueous solution of said chlorides. However, the particles can be tumbled at about 70 F. in an aqueous solution of said chloride or chlorides or in a solution which contains ingredients additional tosaid chloride or chlorides. The invention is not limited to any particular solvent. The invention is therefore not restricted to any particular method of applying the added material or materials to the particles, The invention is not limited to the use of the added material or materials as a mere surface coating upon the particles. If said particles or granules are made of material which has pores or capillary spaces, or which is of an absorbent type, said particles can be wholly or partially impregnated with the added material or materials in addition to being coated. Therefore, the particles can be impregnated without having a perceptible surface coating, or they can be coated without substantial impregnation, or said particles can be both impregnated and coated.

I have also found that it is advantageous to use added material or materials which yield oxygen or oxidizing materials or which exert an oxidizing action in any manner, during the heat treatment. For example, such added materials can be nitrates, such as ammonium nitrate, sodium nitrate, potassium nitrate, etc. I can thus secure better final products, and I can lower the period and/or temperature of heat treatment. Such oxidizing materials penetrate the capillary spaces of the cork and/or cork wood and burn or oxidize the resins or binding materials of the cork and/or cork wood, thus lowering the time of treatment, and also permitting the use of a lower temperature than 600 F. Said resins or binding materials are preferably only partially burned or oxidized. It is well-known that metallic chlorides act as catalysts in decomposing ammonium nitrate, so that the ammonium nitrate decomposes at a lower temperature. Hence, I use said metallic chlorides as catalysts, in addition to utilizing their hygroscopic properties. Some of these chlorides,.such as ammonium chloride, are not hygroscopic. Magnesium chloride and calcium chloride are hygroscopic, in addition to catalyzing the decomposition of ammonium nitrate.

Ammonium nitrate is greatly superior for the purpose of this invention to the other nitrates above mentioned. When ammonium nitrate is heated to a suitable temperature, it is decom' posed and said decomposition is exothermic. Such decomposition therefore provides heat throughout the interior of the mass of material which is being molded under heat and pressure. The internal heat which is thus produced provides quicker and more uniform heating, and it makes it possible to use a baking furnace which is heated, as an example, to 400 F.-450 R, instead of using a baking furnace which delivers heat at a temperature of about 600 F. Hence the exterior of the mass is heated only to 400 EL-450 F., and the heat at the interior of the mass is partially due to exothermic decomposition or reaction.

I also use added hygroscopic materials, such as magnesium chloride, calcium chloride, other hygroscopic mineral salts, glycerine, or other materials of this type which have a high boiling point. This high boiling point is preferably at least 450 F.

The boiling point of glycerine is 290 0., namely 554 F., so that the glycerine is not evaporated, since I can use a heating temperature of less than 290 C. This glycerine may be anhydrous or it may be intermixed with water, as long as all or some of the glycerine is retained in the final molded mass. These hygroscopic materials retain some water in the finished mass of material.

Some examples of the solutions of the added materials which are utilized are as follows, the proportions being by weight:

Example No. 1

Parts Ammonium nitrate 33 Water 67 This formula is suitable for making a shell plug which, as previously stated, must completely disintegrate when the shell is fired. As previously stated, shell plugs are preferably made from particles or granules of pure cork. Enough of said solution is applied to said particles or granules so that the dry weight of the ammonium nitrate which is thus applied is preferably at least substantially 8% to 9% of the dry weight of the cork particles. I prefer that the dry weight of the ammonium nitrate should be substantially 11% of the dry weight of the cork particles, and said proportion can be increased to 16%. That is, after the solution has been applied and the water of said solution has been wholly evaporated, the weight of the residual ammonium nitrate with which the cork granules are coated and/or impregnated, is preferably 11%15% of the original dry weight of the cork particles or granules.

Example N o. 2

Parts Ammonium nitrate 50 Water 50 Parts Ammonium chloride Water 75 This formula is used in manufacturing insulation bodies. The proportion of the dry weight of the ammonium chloride which is added to the cork and/ or cork wood, is preferably the same as in Example No. l, with reference to ammonium nitrate.

Example No, 4

Parts Ammonium nitrate Magnesium chloride (MgClzGHzO) 20 Water 50 Glycerine 10 The above formula is used for making insulation bodies. Excluding water, about one part of the material of this Example No. 4 is applied to 5.5 parts of the particles of raw material, said proportion being by weight. Hence the weight of the added ammonium nitrate is about 7% of the weight of the cork and/or cork wood. This percentage can be varied. This formula of Example No. 4 is particularly suitable for curing the mass of compressed particles of cork and/ or cork wood by means of heat which is applied by short waves. H Example No. 5

Parts Ammonium nitrate Q. 46 Magnesium chloride (MgClzfiHzO) 7.6 Glycerine 7.6 Water 28 This formula is also used for making insulation bodies and for providing applied coating and/r impregnating material by means of which the mass can be cured by short waves. Theweight of the added ammonium nitrate can be as stated in Example No. 4.

Example N0. 6

I Parts Ammonium nitrate 38 Sodium nitrate Water -1 50 Glycerine 7 This formula is also used for making insulation bodies which can be secured by means of short waves.

In this Example No. 6, the total weight of the added nitrates can be 7% of the weight of the cork and/ or cork wood, although this proportion can be varied, as above stated.

Example N o. 7

Parts Ammonium nitrate 50 Ammonium chloride -I 5 Water 45 This example illustrates the proper proportion of ammonium chloride, to serve as a catalyst in the decomposition of the ammonium nitrate.

One part by weight of said solution is sprayed or otherwise applied to three parts by weight of cork and/or cork wood. Hence, if the water of said solution is evaporated, one part of cork heat, without evaporating the water of the solution. If desired, the water in each of the formulas can be wholly or partially evaporated, at 70 F. or at any other suitable temperature, before the particles are subjected to heat and pressure. If the formulas which include hygroscopic materials are utilized, some of the water is always retained. The evaporation of the water can be in any desired proportion. Magnesium chloride and glycerine are examples of hygroscopic materials. The glycerine also exerts an effect upon the particles, in addition to its hygroscopic effect. As previously mentioned, I prefer to apply dry heat without the use of steam or moisture of any kind, although the invention is not restricted in this respect.

The residual materials which are stated in Examples Nos. 4, 5, 6 and '7, after the water has been wholly evaporated, save for the water which is retained by the hygroscopic ingredients, can be readily ionized. As previously stated, the

. trate.

water need not be wholly evaporated. I can therefore cure bodies which are made with the mixtures specified in Examples Nos. 4, 5, 6 and 7, bymeans of electric waves. The block of the particles 01 cork and/or cork wood, to which said mixtures have been applied, is held in suitable compressed form between electrodes which are connected tothe terminals of a suitable generator of I alternating current. The frequency of said alternating current is preferably 10-100 kilocycles. As an example, I can use a current whose wave length is 10 meters, corresponding to a frequency of 30 kilocycles. I thus develop the necessary temperature, whichneed not exceed 450 F., rapidly throughout the entire mass of compressed material, due to the highly ionized added materials, and also due to the exothermic decomposition of the ammonium nitrate or other ni- The use of hygroscopic material is advantageous in retaining sufiicient water in or on the granules, thus facilitating the cure by means of internal heat which is electrically developed, in addition to the heat which is developed by the exothermic decomposition of one of the loading ingredients.

I can thus lower the heating period of 6-12 hours, to 50%-33 thereof. I also produce a finished block of material which is uniformly discolored throughout, whereas, according to present methods, the finished block has maximum discoloration at the surface thereof. I also produce finished blocks of superior resilience, especially with the use of the formulas of Examples 4-6 inclusive.

The finished block can be of any size. As an example, I can make the standard cubical block whose volume is one cubic yard.

Ammonium nitrate begins to decompose at F. and it is fully decomposed at the applied temperature, which does not exceed 450 F. The 1 decomposition of the ammonium nitrate produces water, and it also produces nitrous oxide, which is a good oxidizing agent. I prefer to use ammonium nitrate, instead of potassium nitrate or sodium nitrate. The sodium nitrate and potassium nitrate are more unstable and explosive than ammonium nitrate. I prefer to use the more stable nitrate, which also yields water when it is decomposed. However, the invention is not limited to the use of any particular material which produces internal heat.

The magnesium chloride can be replaced by calcium chloride, which is also a good hygroscopic material. The hygroscopic materials are preferably not decomposed by the applied heat. The finished body of cork and/or cork wood may have any desired density. Such density may be 19-22 pounds per cubic foot, and it may be as low as 8 pounds per cubic foot.

While the invention has its greatest utility in producing bodies which are made of cork and/or cork wood, it applies generally to the manufacture of bodies which are made of cellulose or cellulosic materials, and its application is not limited to any material.

Ordinarily, ammonium chloride volatilizes, without decomposing, at a temperature which is much higher than the maximum temperature of 450 F. which I utilize in my process, as applied to cork and/or cork wood. However, when ammonium chloride is deposited by evaporation from its aqueous solution, in or upon cellulosic material, including deposition in or on cork and cork wood, said freshly deposited ammonium chloride is partially decomposed by the application of gentle heat which is below said maximum temperature of 450 F. When I use ammonium chloride, I prefer to apply the heat and pressure in order to connect the particles to each other, before the water of the solution has wholly evaporated, and immediately after the water or other solvent has been partially or wholly evaporated. Tests have shown that if a writing is made with an aqueous solution of ammonium chloride on paper, and such writing is heated to a relatively low temperature by means of a hot iron, said writing, which is originally colorless, assumes a dark color. This shows that there is some partial decomposition of the ammonium chloride at low temperature which is less than 450 F., when it is freshly evaporated from its aqueous solution, especially if the water of said aqueous solution has not been completely evaporated. Hence, under the conditions stated herein, the ammonium chloride has been found effective by actual tests, even though the maximum operating temperature is below the temperature at which dry ammonium chloride volatilizes. While I can use other chlorides, as previously stated, ammonium chloride is by far the preferred ingredient of its class. Ammonium chloride is ordinarily volatilized at 338 C. (640 F). When it is thus volatilized at 330 C., the vapor is partially decomposed into ammonia and hydrogen chloride. I believe that when ammonium chloride is partially decomposed under the conditions stated herein, there is a liberation of ammonia from the freshly deposited ammonium chloride.

The ammonium chloride which is freshly deposited from its aqueous solution is somewhat acidic, instead of being wholly neutral. I use such freshly deposited ammonium chloride, which pref erably contains some non-evaporated water.

According to the specific embodiment disclosed herein, I do not use any resinous binder or other binder, in addition to the natural resins or binding ingredients of the material. This is the preferred embodiment, especially in making shell plugs. However, I include the use of additional binding ingredients, which can be applied to the particles after they have been coated as described herein. The particles can be first coated with a supplemental binder, and such coated particles can then be coated with the ingredients described herein.

While I have referred to burning or oxidizing the resins of cork and/or cork wood, I prefer that such burning or oxidation should be partial, thus leaving sufi'lcient natural binding material to produce a self-connection between the particles of cork and/or cork wood.

The ammonium chloride is deposited in crystalline form from its aqueous solution. Said deposited ammonium chloride is free from water of crystallization.

I have described preferred embodiments of my invention in considerable detail, but the invention is not limited to any of the details described herein, and numerous changes and omissions and additions can be made in this disclosure, without departing from the scope of the invention. For example, the working temperature, pressure, proportion of added material, etc., will depend upon the composition of the starting material, the desired properties of the finished body, the use of added binders, etc.

I claim:

In the art of connecting to each other a mass of particles which are held in abutting relation under pressure, the material of said particles being selected from a class which consists of cork and cork wood, that step which consists in decomposing ammonium nitrate which is distributed internally and substantially uniformly in said mass, while said particles are thus held in abutting relation, said ammonium nitrate being decomposed by heating said mass to the decomposition temperature of ammonium nitrate.

J OSEF EHRLICH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,607,046 Bentley Nov. 16, 1926 1,598,039 Bentley Aug. 31, 1926 1,105,098 Paschke July 28, 1914 1,008,972 Lenhart Nov. 14, 1911 FOREIGN PATENTS Number Country Date 307 Great Britain 1904 

